The present invention generally relates to an apparatus for coupling attachments to tools and the like, and more particularly to a ferrule for coupling an accessory attachment to a rotary hand tool
There has been continued innovation and improvement in the design of power tools, particularly rotary hand tool units of the type that are used in woodworking, metal working and the like. Examples of such products are those made under the Dremel brand by the S-B Power Tool Corporation of Chicago, Ill., which also produces many accessory attachments for such rotary hand tool units. The rotary hand tool units are generally cylindrical in shape and contain a motor with a rotary output shaft that is adapted to drive the various rotary tool bits, such as small saw blades, sander discs, grout removal tool bits and various other cutting tool bits. There are also may accessory attachments that can be used in association with the rotary hand tool units, with the accessory attachments being connected to the stationary nose end portion of the rotary hand tool unit. Among such accessory attachments is a flexible shaft attachment that conveniently allows the user to operate the various rotary tool bits around corners or in other remote areas of operation. Also useful are grout removing tool guides that conveniently position the grout removing bit relative to the tool guide so that a user can conveniently and effectively remove grout from between individual floor and wall ceramic tiles, for example. As a further example, a depth guide is a desirable accessory attachment that can be used with many types of cutting tools to limit the depth of penetration of the tool into a work piece or work surface.
While such accessory attachments have been available for many years, the manner in which the accessory attachments are coupled to the tool has been the subject of continuing efforts to provide a simple and effective mechanism for coupling or mounting the accessory attachments to the hand tool itself. In this regard, the necessity of tightening holding screws or utilizing multiple turns of a threaded coupling mechanism for coupling the accessory attachment to the rotary hand tool, while effective, are not considered to be particularly simple and convenient in many past designs.
The present invention is related to a particularly simple, elegant and convenient coupling apparatus for attaching an accessory attachment to a rotary hand tool unit of the type that has a housing with a nose portion through which a rotary output shaft extends. The present invention enables a coupling apparatus to be placed on the nose portion in a predetermined position and secured into locking position by a pair of hinged latch members. An accessory attachment can subsequently be attached to the other end of the coupling apparatus, which then serves to couple the accessory attachment to the rotary hand tool unit.
More particularly, the coupling apparatus includes a ferrule that is provided with inwardly protruding ribs or protrusions on opposite sides of the inside of the ferrule, where the ribs engage a pair of outwardly extended elongated arcuate teeth located on the nose portion of the rotary hand tool unit. In this type of hand tool unit, which is adapted to receive another type of attachment mechanism that can be engaged and releases with only a quarter turn of rotation on a pair of teeth, each of the teeth extends approximately 90xc2x0 to 100xc2x0 of the circumference of the cylindrical nose portion and is curved in the axial direction so that the center of the tooth is moved in the axial direction rearwardly or away from the end of the nose end portion. The teeth form a groove portion that extends generally circumferentially around at least a part of the nose portion so that the groove portion is located on opposite sides of the nose portion, coextensive with the elongated arcuate teeth on the nose portion. The preferred embodiment of the present invention has two latch members which are also configured and arranged on the circumference of the ferrule to oppose one another, and each latch member includes an engagement protrusion for engaging the groove portion of the nose portion, and also include a locking protrusion to engage a locking flange located on the external circumference of the ferrule.
Thus, during operation, when the coupling apparatus is slipped onto the nose portion of the hand tool unit, the inwardly protruding ribs align with and engage the elongated arcuate teeth to ensure proper alignment of the accessory attachment with the nose portion. As the latch members are locked into the closed position, the engagement protrusion engages the groove portion of the nose portion. The latch members are finally locked into place by snapping the locking protrusion into the locking flange of the ferrule. The ferrule is also configured so that the latch members, when in the locked position, can be pulled upward into the open position with force enough to overcome the frictional engagement of the locking protrusion and the locking flange, subsequently making the attachment easily releasable by simply pulling the attachment from the nose portion with relatively modest force.